1. Field of The Invention
The present invention relates to a coated granular curing agent and an anchor bolt-fixing composition comprising the same. More particularly, the present invention is concerned with a coated granular curing agent, which is for use in curing a radically curable compound (hereinafter, frequently referred to as a "first radically curable compound") selected from the group consisting of a radically curable resin and a radically polymerizable monomer and which comprises an organic peroxide granule, wherein the organic peroxide granule has an entire surface thereof coated with a layer of a cured resin derived from another radically curable compound (hereinafter, frequently referred to as a "second radically curable compound") which is the same as or different from the above-mentioned first radically curable compound. The present invention is also concerned with an anchor bolt-fixing composition comprising (1) a curable composition comprising at least one radically curable compound selected from the group consisting of a radically curable resin and a radically polymerizable monomer, and a cure accelerator; and (2) a plurality of granules of the above-mentioned coated granular curing agent. The coated granular curing agent of the present invention is advantageous not only in that the curing agent can be handled with ease, but also in that the curing agent can be uniformly dispersed in a radically curable compound, so that it exhibits excellent curing performance. Therefore, the coated granular curing agent of the present invention can be advantageously used as a curing agent for a radically curable resin and/or a radically polymerizable monomer, which is used in various fields, such as a water-transmitting resin mortar and a casting resin. Especially, the curing agent of the present invention can be advantageously used to provide an excellent anchor bolt-fixing composition which not only has a long life, but also is capable of fixing an anchor bolt to a base while enjoying high fixation strength.
2. Prior Art
Conventionally, as a curing agent for a radically curable resin, such as an unsaturated polyester resin, an epoxy acrylate resin or a polyester acrylate resin, various organic peroxides have been used. These organic peroxides are appropriately selected depending on various factors, such as the type of resin to be cured and the ambient temperature at the time of performing curing of the resin. When it is attempted to cure a resin at room temperature or below, the organic peroxide is frequently used in combination with a cure accelerator, such as an aromatic amine.
Radically curable resins, which can be cured using an organic peroxide as a curing agent, have been used in various fields. For example, radically curable resins are used as a resin for providing a corrosion-preventing lining, as a resin for producing a molded article by use of a metal mold and as a resin for use as a main agent for an anchor capsule. (The term "anchor capsule" used herein means a capsule used to fix an anchor bolt or an iron rod to a base, each of which is used in fixing a machine or other structures to bases, such as a rock bed, concrete and masonry.) As a resin to be used as the main agent for an anchor capsule, a radically curable resin, such as an unsaturated polyester resin or an epoxy acrylate resin, is generally used.
Conventionally, the anchor capsule comprises a curable resin in a viscous liquid form, a curing agent, and, optionally, an aggregate. The operation of fixing an anchor bolt or an iron rod to a base using such an anchor capsule is generally conducted by a method comprising inserting an anchor capsule into a hole drilled in a base, and driving an anchor bolt or an iron rod into the hole, thereby breaking the anchor capsule in the hole so as to allow the curing agent to be mixed with the curable resin in a viscous liquid form, so that the resin can be cured. Specific examples of methods for breaking an anchor capsule in a hole by means of an anchor bolt or an iron rod include: a first method, in which an anchor capsule in a hole is broken by driving the anchor bolt or the iron rod into the hole by means of a hammer; and a second method, in which an anchor capsule in a hole is broken by the rotary percussion caused by the anchor bolt or the iron rod which is driven into the hole by means of a hammer drill or the like. When the second method is employed, the anchor bolt can be fixed to the base while enjoying high fixation strength, as compared to the fixation strength achieved by the first method. Therefore, the second method is advantageous especially for fixing an anchor bolt to a base located in sea water or water, or to a base located on a shore, in which a high fixation strength is required.
In the above-mentioned second method, the below-described type of an anchor capsule is generally used. That is, such an anchor capsule has a double-wall structure comprising cylindrical outer and inner casings, each of which is breakable by the action of an anchor bolt or an iron rod when the anchor bolt or the iron rod is applied to the anchor capsule, in which a main agent comprising a curable resin in a viscous liquid form and an aggregate are disposed in a space defined by the inner wall of the outer casing and the outer wall of the inner casing, and in which the curing agent is disposed in the inner casing (see European Patent No. 0 150 555).
Further, Examined Japanese Patent Application Publication No. 4-1160 discloses an anchor bolt-fixing capsule having a double-wall structure comprising outer and inner casings, each of which is breakable by the action of an anchor bolt when the anchor bolt is applied to the capsule, which comprises the above-mentioned outer and inner casings, a curable resin in a viscous liquid form and a mixture of a solid granular curing agent and an aggregate, wherein one of the curable resin and the curing agent-aggregate mixture is disposed in the inner casing, and the other is disposed in a space defined by the inner wall of the outer casing and the outer wall of the inner casing, and wherein the solid granular curing agent and the aggregate are uniformly mixed.
However, in the above-mentioned capsules for use in an anchor bolt-fixing operation, it is requisite that a curable resin in a viscous liquid form and a curing agent be separately disposed by using a double-wall structure. Therefore, the above-mentioned capsule is disadvantageous in that not only is the production process for the above-mentioned capsules cumbersome, but also the dispersion of the curing agent in the curable resin at the anchor bolt-fixing operation is likely to become unsatisfactory and, hence, the curing of the curable resin becomes non-uniform. Further, when a capsule for use in an anchor bolt-fixing operation has a double-wall structure as mentioned above, problems arise such that an operation in which a curing agent in a powdery or granular form is packed into a casing, especially the inner casing (which has a smaller diameter than the outer casing has), is extremely cumbersome and, in addition, the fine powder of curing agent is inevitably scattered in the workshop during the packing operation, thus degrading the working environment. Also, during the packing operation, a bridging of the curing agent occurs in the packing hopper, and in the casing being packed with the curing agent, so that the operation efficiency becomes poor.
An anchor bolt-fixing capsule has been proposed, in which a rod-shaped curing agent and a mixture of a curable resin in a viscous liquid form and a granular stone aggregate are disposed in an opaque cylindrical tubular casing having an opening which is fittedly closed by a transparent plastic cap, wherein the rod-shaped curing agent is a molded product obtained by molding a mixture of a peroxide, an organic binder and a diluent, and has an entire surface thereof coated with a cured resin layer (see Examined Japanese Patent Application Publication No. 63-13000). This capsule solves the problems of such a capsule having a double-wall structure as mentioned above. However, this capsule is disadvantageous not only in that, since the curing agent used therein is in the form of a rod, the curing agent cannot be packed into the casing simultaneously with the packing of the granular stone aggregate, and the packing of the granular stone aggregate can be conducted only after the packing of the rod-shaped curing agent, thus rendering the packing operation cumbersome, but also in that during the packing of the granular stone aggregate, a bridging of the granular stone aggregate occurs between the inner wall of the tubular casing and the rod-shaped curing agent, so that the granular stone aggregate cannot be packed fully to the bottom of the casing. Further, this capsule also poses a problem such that, during the anchor bolt-fixing operation, when the anchor bolt is driven into the capsule by the rotary percussion caused by a hammer drill, the rod-shaped curing agent is broken into pieces, and the pieces will sink to the bottom of the hole (in which the anchor bolt is to be fixed), so that the mixing between the curing agent and the curable resin in a viscous liquid form becomes non-uniform. Hence, a large non-uniformity is caused in the curing of the resin, so that a high anchor bolt-fixing performance cannot be stably obtained.
There is also a proposal for an anchor bolt-fixing cartridge comprising a cylindrical cartridge having a plurality of macrocapsules disposed therein, wherein each of the macrocapsules is filled with a curable polymer, and wherein each of the macrocapsules is in contact with other macrocapsules and/or the inner wall of the cartridge so as to be packed in the cartridge in immobilized fashion (see Unexamined Japanese Patent Application Laid-Open Specification No. 55-32814). According to the method disclosed in this prior art document, the macrocapsules in the cartridge are broken into flakes by the action of an anchor bolt, and the resultant flakes function as a so-called "static agitator" for the curable polymer so that the space between the anchor bolt and the inner wall of the hole is uniformly filled with the curable polymer. However, as can be seen from the above, the macrocapsules used in this technique must be those which are breakable into flakes by the action of an anchor bolt. As such macrocapsules, for example, hollow glass balls coated with a phenol resin, fragments of a clay tube (wherein the fragments have been sealed at both ends thereof), gelatin capsules and the like are used, but materials which can be used for the macrocapsules have been limited. Accordingly, methods for introducing a curable polymer to the macrocapsules are also limited. As such methods, for example, there can be mentioned a method which comprises dipping macrocapsules in a curable liquid polymer, and degassing in situ the macrocapsules in vacuo, followed by increasing the pressure so that the macrocapsules are filled with the curable liquid polymer; and a method which comprises injecting a curable liquid polymer to the macrocapsules by means of a syringe. These methods are, however, disadvantageous because of the low productivity of final macrocapsules containing a curable polymer liquid. Further, in these methods, as can be clearly understood from the above, it is absolutely necessary to use as a curable polymer a curable liquid polymer, and a curable solid polymer, such as a solid polymer in a granular or a powder form, cannot be used.
There is also a proposal for a one-pack type curing resin composition usable as an adhesive, a sealant, a coating material, a molding material and the like, which is in the form of a dispersion of microcapsules in a mixture of a polymerizable polyfunctional acrylate compound (which is a monomer having at least two acrylic acid residues) and/or a polymerizable polyfunctional methacrylate compound (which is a monomer having at least two methacrylic acid residues) as a curing resin component with an organic peroxide as a curing agent, wherein the microcapsules contain a cure accelerator which, when combined with the organic peroxide, is capable of forming a redox polymerization reaction system for the polyfunctional acrylate compound and/or the polyfunctional methacrylate compound, and is coated with a film comprising a hydrocarbon compound capable of forming a coating (see Examined Japanese Patent Application Publication No. 54-32480). However, this one-pack type curing resin composition is disadvantageous in that a gelation of the resin component proceeds unfavorably rapidly since the curing resin component is directly in contact with the curing agent in the reaction system.